Magnetic material



May 15, 1928. 1,669,646

A. F. BANDUR MAGNETI C MATERIAL Filed April 17, 1926 Fyf.

Praia May 15,1928. 1,669,646

UNITED STATES PATENT OFFICE.

ADOLPH FRANCIS BANDUB, OF BERWYN, ILLINOIS, ASSIGNOR TO WESTERN ELECTRIC COMPANY, INCORPORATED, OF NEW YORK, N. Y., A CORPORATION OF NEW YORK.

MAGNETIC MATERIAL.

Application filed April 17, 1926. Serial No. 102,731.

This invention relates to magnetic mate- Fig. 2 shows a plurality of these secrials and magnet cores, and more especially trons assembled to form a completed core. 65

to magnet cores for loading coils for tele- It will be understood, however, that this phone circuits and their method of producis merely illustrative and the invention. is A 6 tion. not limited to the production of this form The principal object of the invention is of core but 1s adapted to the productionof the production of a magnetic element havcores of magnetic particles of many forms. a ing low losses and a relatively high per- In carrying out the present invention, the meability to enable a given inductance to be magnetic material is prepared in the fol- 10 bt i d f a i i nt f t lowing manner: The magnetic material emrial and possessing to a high degree those ployed is preferably prepared from a nickel electrical and magnetic characteristics which Iron alloy commonly referred to as permmake it highly desirable in electrical sigalloy which is treated in a manner more naling apparatus, particularly in loading fully described in the 'copending applicacoils for telephone circuits. tion of G. P. Beath and H. E. Heinicke, In accordance with one embodiment, the Serial No. 101,179, filed April 10, 1926, to present invention contemplates the construcreduce the alloy to a finely divided form. tion of magnet cores of an alloy including Experience has proven that where low eddy nickel and-iron in finely divided form, comcurrent losses are desired it is essential that 20 bined with a suitable insulating material the particles be of small size and preferably and heat treated to have a higher inherent of such size that all of the particles will magnetic permeability and lower inherent readily pass through what is generally hysteresis loss than iron. More specifically, known as a 120 mesh screen and a large the invention contemplates the formation percentage pass through a 200 mesh screen. of the magnet cores of a nickel iron alloy According to one embodiment of the-invenin finely divided form in which the protion, the alloy is prepared by melting apportions of its constituents are more than proximately 78% parts of nickel and 21 80 25% of nickel and the remainder principally parts of iron in an oxidizing atmosphere iron, and in a form which has proven satis and pouring the resulting alloy into a mold. factory the nickel content being approxi- When prepared according to the foregoing mately 78 of the whole. The metal parprocess, the resulting alloy will. be exceedticles are treated With a mixture of a flux, ingly brittle and is therefore particularly such as boric acid and kaolin in colloidal adapted to be reduced to a finely divided or suspension, whereby the alloy particles are dust form from which the finished cores are individually insulated after which they are molded. compressed into cores of the desired shape After the brittle ingots are obtained they and size. The cores are then impregnated are successively passed while hot through with a solution of zinc hydroxide, are heatprogressively reducing rolls which form the ed to expel moisture and finally are heat alloy into flat slabs approximately onetreated to the optimum temperature for the quarter of an inch thick. By the hot rolling particular alloy of which the cores are conprocess the size of the crystalline structure is structed to stabilize the insulator and to materially reduced, which since the disin- 9 give the required permeability, low hysteretegration of the material takes place mainsis losses and highspecific resistance, hence, ly at the crystal boundaries, is essential in low eddy current losses of the rings. I order to have a satisfactory yield of dust.

It is believed that the invention will be The rolled slabs are broken into short pieces clearly understood from the following deand are then crushed in a jaw crusher, tailed description of one embodiment therehammer mill, or any other suitable type of of and from the accompanying drawing, in apparatus in which a further reduction oc- 50 which V curs. The material after being passed Fig. 1 is a perspective view of a section through the jaw crusher is subsequently of a loading coil core made in accordance rolled in a ball mill until it is reduced to a with the present invention, and fine dust. The dust is sieved through a I dried insulated oughly dissolved ring mesh sieve and any residue is remelted and the foregoing operation is repeated to again reduce the material to a finely divided form. Prior to the addition of the insulating material, the finely divided particles of the nickel iron alloy are annealed in a closed container at a temperature of approximately 750 C. to 980 0., the temperaturepf about 925 C. having proven to be OIIE WhICh produces very satisfactory results. It is then necessary to again reduce the annealed alloy which is now in the form of a cake to a fine- 1y divided form, after which it is mixed with the insulator.

According to one form of the invention, the insulator for the dust particles is preared by mixing the ingredients'in the follbwing manner: One part of kaolin is thorin three parts by weight of water by heating to approximately 95 and stirring thorou hly until it forms a th1n homogeneous colloidal mass. To this is added a quantity of a flux such as boric acid equal to four per cent by weight of kaolin to lower the fusion temperature" and to increase the adhesive uality of the kaolin, the boric acid preferab y being dissolved in the hot distilled water in which the kaolin is mixed. The powdered permalloy dust is added to this mixture, the amount of dust being determined by the permeability desired and the particular use to which the finished cores are to be put. The dust is thoroughly mixed with the kaolin solution by thoroughly stirby hand or by rolling in a revolving drum, the temperature of this mixture being maintained at about 100 C. until all of the mechanically held water is removed. The dust particles are then in a form suitable for pressing into cores or rings which are preferably formed with a pressure of approximately 200,000 pounds per square inch. A high pressure is used in forming the rings in order to increase their density, since it has been found that the permeability of the rings increases with increased density.

The pressed rings are impregnated in a solution of zinc hydroxide containing an excess of ammonia for a period of from two to six minutes, depending on the size of the core, in order to allow the insulator to redistribute itself around the individual dust particles. The zinc hydroxide thus added decomposes at the high temperature of the subsequent annealing process and forms an oxide coating on the particles. The rings are then dried in the open at 100 C. for several hours to remove the hygroscopically held water and ammonia, after which they are placed in an oven and heated at approximately 290 C. for several hours, to reduce the amount of chemically combined-water. After the rings are dried, they are annealed preferably in closed pots at the optimum annealing temperature of approximately 7 Lemme 675 C. to artly fuse the kaolin and to give the rings t e greatest permeability ossible consistent with low core losses. A ew test rings may be made of dust insulated in the above manner and their permeability measured. Should their permeability be too low, it may be increased by the addition of a predetermined amount of uninsulated dust or dust which has a light coating of insulation to the insulated dust before it is pressed into rings.

A plurality of rings thus formed are stacked coaxially to form a core on which the usual toroidal winding is applied, the number of such rings used depending upon the existing electrical characteristics of the telephone circuit with which the loading coils are to be associated.

Although the permalloy particles have.

been described as being insulated with a solution of boric acidand colloidal kaolin in definite proportions, it is of course to be understood that the proportionsof the ingredients may be varied without departing from the spirit and scope of the invention. Also other flux materials, such asborax, common salt or magnesium sulphate may be substituted for the bor'ic acid to lower the fusion temperature of the kaolin.

By using an alloy of the proportions stated in the preceding paragraphs and by following the foregoing method of insulating the individual alloy particles and compressing the particles into cores or rings, magnet cores or rings are produced which have extremely desirable electrical characteristics with a minimum amount of material employed. By the use of such cores or rings, inductance units having a higher permeability with equal or less hysteresis and eddy current losses as cores constructed according to previously known methods, but with much less core volume and much less coil volume, are available. 1

What is claimed is:

1. As a new article of manufacture, a magnetic substance composed of particles of a magnetiematerial, and an insulating material consisting of kaolin and a flux separating the particles.

2. As a new article of manufacture, a magnetic substance composed of particles of a magnetic material, and an insulating material consisting of one part kaolin and 4/100 parts boric acid separating the particles.

3. As a new article of manufacture, a magnetic substance composed of particles of a magnetic alloy of nickel and iron, and an insulating material consisting of kaolin and boric acid separating the particles.

4. As a new article of manufacture, a magnetic substance composed of finely divided particles of an alloy of nickel and iron, and an insulating material consisting principally iron, and

' ticles, heating the particles,

of 1 part kaolin and 4/100 parts boric acid separating the particles.

5. As a new article of manufacture, a magnetic substance composed of finely divided particles of a magnetic alloy composed of more than 25% nickel and the remainder an insulating material consisting of kaolin and boric acid separating the particles.

a new article of manufacture, a magnetic substance composed of finely divided particles of a magnetic alloy composed of more than 25% nickel and the remainder principally iron, and an insulating material consisting of 1 part kaolin and 4/100 parts.

boric acid separating the particles.

7. The method of making magnetic structures, which consists in coating particles of a magnetic material with an insulatin material, consisting of kaolin and boric acid, and forming a mass of such insulated particles into a homogeneous solid.

8. The method of making magnetic structures composed of an alloy, which consists in reducing the alloy to finely divided particles, coatlng the particles with an insulating material of kaolin and boric acid, and forming a mass of such insulated particles into a homogeneous solid.

9. The method of making magnetic structures composed of an alloy, which consists in reducing the alloy to finely divided paragain reducing the product so obtained to finely divided particles, coating the particles with an insulating material comprising kaolin and boric acid, and forming a mass of such insulated particles into a homogeneous solid.

10. The method of making magnetic structures composed of an alloy, which consists in reducing the alloy to finely divided particles, heat treating the particles, reducin the product so obtained to finely divided particles, coating the heat-treated particles with an insulating material comprising kaolin and boric acid, forming a mass of such insulated particles into a homogeneous structure, drying the structure and heating it to a high temperature to improve its magnetic properties.

11. The method of making magnetic structures composed of a nickel iron alloy, which consists in reducing the alloy to finely divided particles, heat treating the particles, reducing the product so obtained to finely divided particles, coating the heat-treated particles with an insulating material comprising substantially 1 part kaolin and 4/100 parts boric acid, and forming a mass of such insulated particles into a homogeneousstructure.

12. The method of making magnetic structures composed of an alloy of more than 25% nickel and the remainder principally thereafter heating iron, which consists in reducing the alloy to finely divided particles, heat treating the particles, reducmg the product so obtained .to finely divided particles, coating the heattreated particles with an insulating material comprising kaolin and boric acid, and formmg a mass of such insulated particles into a homogeneous structure.

13. The method of making magnetic structures composed of an alloy of more than and subjecting it to temperature.

14. The method of tures composed of 25% nickel and the remalnder iron, which consists in reducing the alloy to finely divided particles, heat treating the particles, reducing the product so obtained to finely divided particles, coating the heattreated particles with an insulating material comprising substantially 1 part kaolin and 4/100 parts boric acid, forming a mass of such insulated particles into a. homo eneous structure, drying the structure, and eating it to a high temperature to improve its magnetic properties.

15. The method of making magnetic structures, which consists in treating particles of a magnetic alloy with a solution of zinc hydroxide so as to form an oxide coating on the particles.

16. The method of making magnetic strucreat treatment at a high making magnetic strucprincipally g tures, which consists in treating particles 18. The method of making magnetic structures from finely divided magnetic material, comprising coating the individual particles with an insulating material which retains its insulating properties at temperatures up to at least 800 0., compressing the insulated particles into a homogeneous solid, and

said solid to atempera g mogeneous structure, drying said structure,

an alloy of more than temperature,

ture between 450 C. and 800 C. and cooling, to restore the magnetic properties lost in the pressing operation.

19. The method of making magnetic structures from magnetic material in a finely divided form, which consists in heat treatin the particles of magnetic material at a big 1 coating the particles Withan insulator which retains its insulating, properties at high temperatures, compressing the coated particles into a homogeneous solid, and thereafter heat treating the particles at a temperature to impart thereto the desired magnetic properties.-

20. The method of making magnetic structures from a magnetic material of nickel and iron in a finely divided form, which consists in heat treating the particles at a high temperature to prepare them for subsequent operations, coating the particles with an insulating material, and compressing the coated articles into a homogeneous solid.

21. T e method of making magnetic structures from a magnetic material of nickel and iron in a finely divided form,- which consists in heat treating the particles at a temperature approximately 750 C. to 980 \C. to prepare them for subsequent operapermeability, and compressing the mass into a homogeneous solid.

In witness whereof, I hereunto subscribe my name this 1 day of April A.'D., 1926.

ADOLPH FRANCIS BANDUR' 

